[Asterisk-Users] Faxing..not 100%

[Peter Svensson]

On Tue, 7 Dec 2004, Lee Howard wrote:

> On 2004.12.07 10:06 Matthew Boehm wrote:
> > Here is the setup:
> > 
> > POTS -> PRI -> Asterisk -> ATA (Fax)
> > 
> > The ATA is set to only 711. Asterisk's sip.conf sets this device to
> > only
> > 711. Yet, faxing works less than 50% of the time.
> 
> I have a couple of different fax arrangements with Asterisk.
> 
>    POTS -> Asterisk (X100P) -> ATA -> Fax Modem (HylaFAX)
> 
> Probably the *only* reason I can get anything through this arrangement 
> reliably is due to the Class 1 ECM support of HylaFAX.  I see lots and 
> lots of ECM frame data errors, and the sender has to resend them, and 
> the faxes take longer than they should.  There are still often problems 
> due to a lack of synchronicity between the sender and the receiver, but 
> most of the time everything works out.

An extra a-d-a conversion step will cause problems. Running a fax over 
voip even more so most of the time. The timing is not locked end-to-end 
and while this may be acceptable for voice it is a big problem for data.

>    POTS -> PRI -> Asterisk (TE405P) -> Patton T1 Fax Card (HylaFAX)
> 
> This is a nearly flawless arrangement when receiving.  I don't have any 
> problems with it, at least to any extent that I've noticed yet.

Here you have an all digital path, with clocking locked end-to-end, or at 
least from the remote central office all the way to your fax card. 

Peter